The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having lightly doped drains (LDDs).
To increase the aperture ratio of a low temperature liquid crystal display device, the channel length between the source/drain regions must be reduced. When channel length is reduced, however, short channels effect occurs. A hot electron effect also occurs when the device is driven by a voltage.
With a short channel, depletion regions between the source/drain regions become narrow when voltage is applied to the device. Meanwhile, leakage current between the source/drain electrodes occurs, and the punch-through effect intensifies. The electronic properties of a low temperature poly silicon liquid crystal display device are thus affected and the device may be unreliable.
In a typical process of fabricating a lightly doped drain, although the P-type LDDs surround the N-type LDDs, leakage current and punch-through effects still occur when a large voltage is applied to the device.
Accordingly, a liquid crystal display capable of ameliorating the described problems is desirable.